The present invention relates to a substrate processing apparatus; and, more particularly, to a substrate processing apparatus capable of suppressing oxidation and contamination of a substrate under processing.
In a semiconductor device manufacturing factory, there have been widely employed batch-type vertical hot-wall furnaces (from now on, referred to as furnaces) in a thermal process such as an annealing, an oxide film forming, a diffusion or a thin film forming process on a semiconductor wafer.
U.S. Pat. No. 4,770,590 discloses one of such furnaces. In this furnace, a boat exchanger is installed between a wafer transfer unit and the space just under a process tube and there are mounted a pair of boats on a turning table of the boat exchanger, wherein a processed boat is substituted with an unprocessed boat by turning the pair of boats by 180xc2x0 on the turning table with respect to a boat elevator. Namely, in this furnace, while one boat (a first boat) accommodating a set of wafers is processed in the process tube, new wafers (unprocessed wafers) are mounted on the other boat (a second boat) and then transferred by a wafer transfer unit to thereby enhance a throughput thereof.
In this conventional furnace, however, impurities, e.g. contaminants, may be produced during the exchange operation of the boats. Further, since the boats are not fixedly mounted on the turning table, it may be possible that the boats may fall down during the exchange operation thereof or due to an external impact, e.g., an earthquake.
Further, Japanese Patent Laid Open Publication No. 9-289173 discloses a vertical hot-wall furnace including a first boat elevator for mounting and transferring a first boat having wafers mounted thereon between a wafer transfer region and a process tube and a first boat elevator for mounting and transferring a second boat having wafers mounted thereon between the wafer transfer region and the process tube, wherein a boat exchange operation is not executed with respect to a boat elevator such as one disclosed in the above-mentioned U.S. Pat. No. 4,770,590 to thereby enhance a throughput thereof.
Meanwhile, in the a vertical hot-wall furnace disclosed in the Japanese Patent Laid Open Publication No. 9-289173, since the boat exchange operation is not executed with respect to the boat elevator, there entails no position deviation problem and accordingly, the boat capsize problem is prevented. However, since a center position of a heat processing chamber is located on a straight line passing through a position of the first boat elevator and a position of the second boat elevator, a distance between the first boat elevator and the second boat elevator becomes about two times of each arm (rotating unit) of the boat elevators.
This requires an increase a horizontal width (opening) of the vertical hot-wall furnace to thereby increase a dimension thereof. Further, since wafers in the first and second boats transferred from the process tube to preset positions apart therefrom by the first and second boat elevators are carried by a wafer transfer unit, the carrying area of the wafer transfer unit becomes larger and accordingly, footprint (occupying area) thereof becomes large.
It is, therefore, an object of the present invention to provide a semiconductor manufacturing apparatus capable of preventing or reducing generation of impurities and avoiding the tripping or the falling down of boats.
Another object of the present invention is to provide a semiconductor manufacturing apparatus capable of preventing unprocessed boats from being affected by the heat generated from processed boats.
In accordance with a first preferred embodiment of the present invention, there is provided a substrate processing apparatus comprising: a process tube for processing a plurality of substrates; two boats for accommodating the substrates; two boat elevators, each having one boat mounted thereon, the boat elevators carrying the boats between a first position located below the process tube and two corresponding second positions and loading and unloading the boats into and from the process tube at the first position; and a substrate transfer unit for loading and unloading the substrates into and from the boats when the boats are at the first position, wherein a center position of the process tube is disposed inside a triangle formed by connecting the substrate transfer unit and the two boat elevators.
In accordance with the first embodiment, since a center position of the process tube is disposed inside a triangle formed by connecting the substrate transfer unit and the two boat elevators, the space between the two boat elevators can be saved to thereby decrease a horizontal width of the substrate processing apparatus. Further, since the substrate transfer unit can transfer wafers accommodated in any of the two boats at the first position, wafers can be transferred with respect to any of the two boats at one heat treatment stage. This results in saving of a moving area of the substrate transfer unit to thereby decrease the footprint thereof.
In accordance with a second preferred embodiment of the present invention, there is provided a substrate processing apparatus comprising: a substrate processing apparatus comprising: a process tube for processing a plurality of substrates; two boats for accommodating the substrates; two boat elevators for carrying the boats between a first position located below the process tube and two corresponding second positions and loading and unloading the boats into and from the process tube at the first position; and a substrate transfer unit for loading and unloading the substrates into and from the boats, wherein the boat elevators are located at both sides of a line passing through a center of the process tube and the substrate transfer unit and one of the boats is moved by its corresponding boat elevator toward the substrate transfer unit from the first position and the other boat is moved by its corresponding boat elevator toward the opposite side of the substrate transfer unit from the first position.
In the second embodiment, the boat elevators are located at both sides of a line passing through a center of the process tube and the substrate transfer unit and one of the boats is moved by its corresponding boat elevator toward the substrate transfer unit from the first position and the other boat is moved by its corresponding boat elevator toward the opposite side of the substrate transfer unit from the first position. As a result, a horizontal width and a footprint of the substrate processing apparatus can be saved.
In accordance with the first and second embodiments, since the boat elevator can transfer the boats between the first position located below the process tube and the two corresponding second positions, the boat fixedly mounted on the boat elevator can be loaded and unloaded into and from the process tube. Accordingly, the generation of impurity particles can be avoided when a processed boat and an unprocessed boat are exchanged. Further, a capsize problem can be overcome during the exchange operation or an earthquake generation.
In accordance with a third preferred embodiment of the present invention, there is provided a substrate processing apparatus comprising: two process tubes for processing a plurality of substrates; four boats for accommodating the substrates; four boat elevators, each boat elevator for loading and unloading one of the boats into and from one of the process tubes and carrying said one of the boats between one of two first positions below the process tubes and one of three corresponding second positions; and a substrate transfer unit for loading and unloading the substrates into and from the boats.